Fifty million Americans are infected with herpes simplex virus type 2 (HSV-2), but 80-90% of those infected are unaware that they carry HSV-2 [CDC, 2010; Paz-Bailey et al., 2007; Xu et al., 2006]. Regardless of whether patients have visible symptoms or not, they may shed infectious virus and transmit HSV-2 to sexual partners [Rattray et al., 1978; Tronstein et al:, 2011; Wald et al., 2000]. Antiviral drugs reduce, but do not eliminate, the risk of HSV-2 transmission [Sperling et al., 2008; Handsfield et al., 2007; Corey et al., 2004; DeJesus et al., 2003]. Patients who know they carry HSV-2 may take proactive steps to reduce the risk of transmission including antiviral drugs, condoms, disclosure to partners and awareness of subtle symptoms, all of which are effective tools in transmission reduction [Gupta et al., 2007; Rana et al., 2006; Warren, 2002; Wald et al., 2001].
The serological tests used to confirm a diagnosis of HSV-2 infection are imperfect. The most significant problems include (1) the HerpeSelect® HSV type-specific serological ELISA assay (Focus Diagnostics, a wholly-owned subsidiary of Quest Diagnostics, Inc.) may return false-positive results and (2) the confirmatory HSV Western blot test (i.e., the gold standard of HSV serology tests [Warren et al., 2011]) may return “indeterminate” results.
Patients with the potential for false-positives on the HSV-2 ELISA often score as “low-positives” with an index value of 1.1 to 3.5; 50% of these patients prove to be false-positive on the confirmatory HSV Western blot. However, confirmatory Western blot testing fails to resolve the serological status of about 50% of patients who obtained HSV-2 “low-positive” results from the HerpeSelect® ELISA test. Rather, Western blot testing typically returns indeterminate results for these patients. Thus, current HSV-2 serological testing leaves 2-4% of patients with ambiguous results [Ng'ayo et al., 2011; Golden et al., 2005], which for the purposes of this document are referred to as a “HSV-2 indeterminate” diagnosis.
Having an indeterminate diagnosis leaves patients wondering if they are infected with HSV-2, and causes needless anguish in patients who are not infected [Warren, 2002; Warren and Ebel, 2005]. Patients with an indeterminate diagnosis are forced to deal with the ramifications of a bona fide HSV-2 infection; specifically, they feel compelled to disclose their “HSV-2 status” to potential sex partners, risking possible rejection; they may take daily antiviral therapy to reduce the risk of infecting others; and they believe themselves to be 3 times more likely to acquire HIV infection than someone who does not have HSV-2 [Vergidis et al., 2009; Lingappa and Celum, 2007]. Repeat testing often fails to resolve their diagnosis, and thus patients may not know their HSV-2 infection status for months or years; this can have a profoundly negative impact on patients' self-perception and their quality of life.
There is thus an unmet need for an improved serological assay for diagnosis of HSV-2 infection that minimizes, or eliminates, HSV-2 indeterminate diagnoses. The present invention is a novel, flow cytometry-based serological assay that measures the affinity of serum antibody-binding to virus-infected cells (ABVIC) and is believed to be a more definitive HSV-2 serological test.